[css-fonts-4] Should transform/zoom affect optical sizing?

[kojiishi]

I'm investigating what changes should cause a) just re-paint, b) re-measure glyph bounds, or c) re-shape.

Are there any OpenType features that require re-shape when transform/zoom changes? Should this be defined, or should this definition belong to OpenType?

Thoughts appreciated. /cc @litherum @drott @eaenet

[litherum]

@robmck-ms wrote up a great description of Microsoft's research here. I attempted to follow his advice when implementing this in WebKit.

[kojiishi]

Thank you, I wasn't aware of that but yes, this is a great description!

I think this is dup to #807 then.

[fantasai]

Reopening to suggest that advice be informatively either incorporated or linked from a relevant spec somewhere so that other implementors can find it. :)

[litherum]

The advice is incorporated. 3911bf2